The full depth on-site cold recycling construction process requires the crushing and mixing of the entire thickness of the asphalt surface layer in the asphalt pavement and the predetermined proportion of the underlying layer, in order to provide upgraded and uniform base material maintenance technology. If the old material does not have sufficient mechanical properties and structural strength to carry the expected load, then new aggregates need to be added to it, and a certain proportion of chemical stabilizers need to be added to achieve the expected effect.
In the process of full depth on-site cold regeneration construction, it is necessary to ensure that the lower bearing layer of the regeneration layer is intact and undamaged, and its thickness should not be less than 10cm. At the same time, it is also necessary to meet the strength requirements of the structural layer as much as possible. In the full depth in-situ cold regeneration technology, the thickness of a single compacted layer should be controlled between 15-25cm when using cement and lime. When emulsified asphalt and foam asphalt materials are used, the thickness should be controlled within 8~16cm. If the thickness of the single-layer cold regeneration layer is too thick, there will be problems when compacting the layer, causing the relevant equipment to be unable to compact the layer, especially the lower layer, which is less likely to be compacted. In the recycled layer that meets the compaction requirements, in addition to meeting the average compaction requirements, the density difference between the surface 5cm and the bottom 5cm should be controlled within 2%. Of course, double-layer regeneration can also be chosen during the construction process, which requires milling the surface material with a certain thickness, then conducting on-site cold regeneration on the underlying road surface, and then mixing and fusing the milled surface material before laying. The double layer recycled layer laying is not limited by the thickness previously described.
(2) Mechanical facilities and equipment used in full depth on-site cold regeneration construction
When using the full depth on-site cold regeneration construction process, there is no need to use large mechanical equipment. The main mechanical equipment used includes regeneration equipment, stabilizer adding equipment, graders, and rollers.
The main function of the cold regeneration machine is to crush and recover materials, and it occupies a major position in the operation of the full depth on-site cold regeneration construction process. The cold recycling machine can crush and mix asphalt pavement and underlying layer materials with a thickness of 30cm. In the cold regeneration equipment, tungsten carbide toothed cutting tools that can be replaced should be installed in the drum, and manual and automatic operation devices should also be installed. In addition, this equipment should be able to effectively adjust the rotation speed of the drum to adapt to the crushing and mixing of materials with different thicknesses.
In addition, if the moisture content of recycled materials does not meet the established standards, it is necessary to make them meet the established moisture content standards during the drying process. In addition, if the recycled materials are too dry, it is also necessary to replenish the moisture. The cold regeneration machine can be equipped with corresponding water nozzles to add water to the recycled material. During the process of crushing and stirring the recycled material, water can also be added, and adding water at this time can also better estimate.
When adding stabilizers to recycled materials, if the added stabilizers are in powder form, then a quantitative spreading of the material is required. Dry powder stabilizer can be added during the crushing of asphalt layer pavement or before the cold recycling machine mixes the recycled material. Insufficient stabilizer for powdery materials can be affected by weather factors, and in addition, it is prone to generate dust and mist during quantitative paving and spreading operations, which has a great impact on construction operators and the environment. When the stabilizer is added to the cold regeneration machine in a liquid state, the accompanying computer liquid addition system needs to accurately calculate the amount of each liquid added, and there is also a positive interlock system related to the forward speed of the cold regeneration machine, so that the amount of liquid stabilizer added changes with the operation of the cold regeneration machine.
After the cold regeneration machine completes the task of crushing and mixing fusion, it needs to be applied to the grader for laying and shaping operations. In the laying of recycled materials, there is a strict demand for their thickness, so the selection of rollers will be biased and large. Therefore, through the action of a roller, the laying of recycled materials can be more complete and natural, and the required amount of tasks can be successfully completed. This ensures that the paved road surface can meet the usage requirements and bear the expected design load and load.
(3) Full depth on-site cold regeneration construction technology
Firstly, construction layout should be carried out to check the preparation status of mechanical facilities and equipment related to full depth on-site cold regeneration, as well as the preparation status of materials. Then, the freezing operation and laying of cement should be carried out. In this step, a detailed inspection of the cement dosage is required. Next, use a cold recycling machine to add water for mixing work. This step also requires checking the cement dosage and water consumption. It is necessary to use relevant materials according to the specified standards and requirements. After mixing is completed, it is laid on the road surface and preliminary rolling is carried out using a sheep horn roller. During the rolling process, the thickness needs to be tested and operated according to relevant requirements. Next, use a land leveler for flattening operation. In this step, additional watering is required, and construction personnel should cooperate with the land leveler for flattening operation to avoid missing operations in some areas. Then, a smooth wheel roller is used to re press the road surface that has been pressed by the grader. After re pressing, the rubber wheel roller needs to perform a final press, and during this process, it is necessary to check whether the various indicators of the road surface meet the design requirements. After all the above operations comply with the operating specifications and various indicators, it is necessary to place a safety anti-collision cylinder on the repaired asphalt pavement and cover it with geotextile for health preservation, in order to better put it into use in the future.
When using the full depth on-site cold regeneration construction process, it is necessary to first equip the mechanical equipment according to the various mechanical equipment required during the construction process, in order to ensure that the process is carried out in an orderly manner and avoid the occurrence of confusion. After the necessary facilities and equipment are in place during the construction process, it is necessary to calculate the amount of various materials needed. For example, when adding cement stabilizers in a dry powder form, the required amount of cement should be calculated first. The formula is: cement dosage (kg/㎡)=compacted thickness (m) × Maximum dry capacity (kg/m?) × Compaction degree (%) × Cement dosage (%)/(1+cement dosage (%)). Calculate the cement dosage using this formula, and then calculate the cement stabilizer dosage.
In the process of fully deep on-site cold recycling construction, a pre laid material can also be used, in which the length of the pre laid cement needs to be controlled to ensure the normal operation of the cold recycling machine when mixing the recycled material. In addition, the length of pre distribution also needs to be determined based on the driving speed of the cold recycling machine, as well as the size of the road slope and cross slope. In general, the pre distribution length is 80-150 meters. It is best to carry out the distribution operation while the cold recycling machine is stirring the recycled material to avoid pollution caused by passing vehicles driving too fast during the process, which also causes certain losses and waste of materials.
In the process of using the full depth on-site cold recycling construction technology to repair the road surface, there is generally a certain gap between the width that the cold recycling machine can handle and the width of the road surface. Therefore, multiple crushing operations are required to treat the asphalt road surface that needs to be repaired, which can cause multiple longitudinal joints and some overlapping phenomena on the road surface.
The working speed of cold revitalization has a great impact on how much asphalt pavement can be repaired in a day. The thickness and hardness of asphalt pavement, as well as the thickness of the underlying layer that needs to be added to the recycled material, the requirements for the recycled material, and the production capacity of the cold recycling machine will all have a certain impact on the working efficiency of the cold recycling machine.